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3-1
Chapter 3
Operational Theory
Before you jump in and start writing a complex host program, it might be nice to
be familiar with the theory behind the operation of your RF Terminal.
Basic RF System communications…
A WIFI RF Terminal system consists of three components – Host Server,
Access Points and RF Terminal. The Access Points are connected to the Host
Server by Ethernet wiring. The RF Terminal "signs in" by establishing
communication with a Server Program (located on the Host Server) through an
Access Point. After the RF Terminal "signs in", the Server Program can send a
prompt to the terminal with the ActiveX program interface provided by Worth
Data. The application running on the Host Server sends a data prompt to the RF
Terminal device to the Access Point (using the Ethernet wiring), and then by
radio link to the terminal device. The RF Terminal displays the data prompt on
the display and waits for the operator to enter the requested data. Once the
operator enters his data, the RF Terminal transmits the data to the Access Point,
which in turn passes it on to the Host Server. The application on the Host
Server processes the information and sends a new data prompt out to the Access
Point and the whole process begins again.
A little more in depth…
This RF system’s dialogue is Terminal initiated. The Terminal says, “I’m
here, give me something to do.
When you select DEVICE SIGN ON?, the RF Terminal first establishes
communication with the network as follows:
1. It looks for an Access Point with an identical SSID and WEP Key using
the Channel Number in its configuration as the starting channel.
2. If the terminal is configured to obtain its IP address from a DHCP
Server, it requests an IP address from a DHCP Server. If it requests an
IP address, the terminal will display:
Looking for DHCP Server,
Please Wait
3. If the terminal does not have a fixed Server IP address configured, it
does a search for an Application Server. While is searches for an
Application Server, the terminal will display:
Looking for App Server,
Please Wait
4. Now the RF Terminal sends a SIGN ON message to the application
Server. All messages include data as well as the transmitter's and
receiver's MAC address, IP address, and Port address.